Air cooled shrink tunnel curtain



United States Patent 3,242,590 AIR COOLED SI-RINK TUNNEL CURTAIN Donald E. Witt, Canandaigua, N.Y., assignor to National Distillers and Chemical Corporation, New York, N .Y., a corporation of Virginia Filed Aug. 27, 1962, Ser. No. 219,470 4 Claims. (Cl. 34-242) This invention relates to a novel curtain for the entrance and exit openings of a shrink tunnel and more specifically relates to an air cooled curtain of porous cloth pockets which are filled with air under pressure which seeps through the cloth.

Shrink tunnels are well known in the art and are gen erally comprised of an oven in which a body wrapped in a heat sensitive plastic film is placed to cause the film to shrink so as to form a tight package. Typical film wrappings are films of polyethylene or polypropylene having thicknesses of the order of /2 mil. These ovens generally include a neoprene rubber conveyor belt or a belt of glass fiber impregnated with silicon rubber means for carrying the articles through the oven.

Both the entrance and exit openings of the oven, or so-called shrink tunnel, are commonly provided with silicon rubber curtains to prevent the escape of heat to the external environment. By way of example, the tunnel may be used in a low temperature meat storage room where low temperature must be retained.

When the curtains have been formed of the silicon rubber or other similar material, the curtains become extremely hot. It has been found that as materials wrapped in plastic film pass through the heated curtains, and particularly the exit curtain, holes are melted in the plastic film as it drags beneath the curtain,

The principle of the present invention is to provide a novel curtain of a porous cloth formed in one or more pockets. Air is then forced into the pockets and escapes by seeping through the porous cloth material. Thus, the

curtains are air cooled and are sufficiently flexible to per-- mit packages wrapped in film to force the curtains aside as they move into and out of the shrink tunnel on the conveyor. Since the curtains are now cooled, they will not burn holes in the thin plastic film.

Accordingly, a primary object of this invention is to provide a novel cloth curtain for a shrink tunnel.

Another object of this invention is to provide a novel curtain, which is air cooled, for a shrink tunnel.

A further object of this invention is to provide a curtain for a shrink tunnel which will not adversely affect thin plastic film which wraps objects which are passed through the tunnel.

Another object of this invention is to provide a novel curtain, which is cooled by external cooling means, for a shrink tunnel.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings in which:

FIGURE 1 shows a side view partially in cross-section of a shrink tunnel adapted with the novel cloth curtain of the invention.

FIGURE 2 shows a front view of the shrink tunnel of FIGURE 1.

FIGURE 3 shows a perspective view of the cloth curtains used for the shrink tunnel of FIGURES 1 and 2.

Referring now to FIGURES 1 and 2, there is illustrated a side view of an oven which may be of any typical construction and can be heated by an appropriate heating coil 11 contained in the top of the oven. A conveyor belt 12 is contained in the floor of the oven to pass packages from the front opening 13 of the oven which is guarded by curtain 14 to the rear opening of the oven which is guarded by curtain 15. Appropriate conveyors 16 and 17 which have elongated rollers may be provided for the handling of the packages which are to be passed to conveyor 1-2 within the oven.

These packages are normally wrapped with any Well known type of plastic film which has ben prepared in such a manner that the application of heat will cause the film to shrink to provide a neat, tight package.

The curtains 14 and 15 which guard the entrance and exit respectively of the shrink tunnel are constructed in a manner best shown in the perspective view of FIGURE 3. Generally, an elongated porous bag which is of a porous cloth material such as cotton has a plurality of pleated pockets 20, 21, 22 and 23 formed therein as by stitching such as stitching lines 24, 25 and 26. The stitch lines do not extend to the bag bottom so that the bottom of the curtain forms a horizontal pocket 27 which communicates with all the pockets 20, 21, 22 and 23. The upper section of the curtain assembly is then formed of a frame 30 which could be of steel which received the open end of the cloth curtain as by a tape which adheres to the upper open end of the curtain and the bottom of the steel frame.

The steel frame 30 is then provided with screw openings such as openings 32 and 33 which permit securing of frame 31 to the upper portions of the entrance and exit windows. The steel frame 30 of each of curtains 14 and 15 of FIGURE 1 is then connected to suitable ducts such as ducts 14a and 15a whereby frame 30 of curtain 14 is connected to compressor 34 which can be carried in the top of oven frame 10 while the steel frame of curtain 15 is connected to duct 15a extending from compressor 35. Each of compressors 34 and 35 is of suflicient size to generate a flow of air which could be of the order of 12 cubic feet per minute where this air seeps through curtains 14 and 15 respectively to cool the cur tains,

Clearly the compressors 34 and 35 will cause pockets 20 and 21, 22 and 23 of FIGURE 3 to expand to their greatest dimension with the curtain being held in shape by the sewn lines 24, 25, 26 and by the connection of the open ends of the curtain to the steel frame 30.

Since the curtain is formed of a cloth material, it is clear that as an article passed through the curtain it will cause the curtain to swing upwardly about the steel frame 30. Moreover, since the curtains are air cooled, the rubbing of the plastic film wrapping on the articles passing into the oven will not be adversely affected since the surface of the curtains will be at a relatively low temperature.

Although preferred embodiments of the novel invention have been described above, many variations and modifications will now be obvious to those skilled in the art, it is preferred therefore to be limited not by the specific disclosure herein but only by the appended claims.

What is claimed is:

1. A flexible air cooled curtain for an opening in an oven; said flexible air cooled curtain comprising a plurality of closed pockets of a porous textile fabric; said plurality of closed pockets having connecting means for connecting the interior of said pockets to a source of air under positive pressure; said pockets being formed by parallel sewn lines extending from the open top of a cloth bag; said porous textile fabric permitting air seepage therethrough at approximately 12 cubic feet per minute.

2. A flexible air cooled curtain for an opening in an oven; said flexible air cooled curtain comprising a plurality of closed pockets of a porous textile fabric; said plurality of closed pockets having connecting means for connecting the interior of said pockets to a source of air under positive pressure; said pockets being formedby parallel sewn lines extending from the open top of a cloth bag; the open top of said cloth bag being secured to a metallic frame adapted to retain said bag open at its said top; said source of air being connected to said pockets at said frame; said porous textile fabric permitting air seepage therethrough at approximately 12 cubic feet per minute.

3. In a shrink tunnel, said shrink tunnel having an entrance opening and an exit opening; each of said entrance openings and exit openings being closed by a respective flexible curtain of a porous fabric material; each of said flexible curtains being air cooled; each of said flexible air cooled curtain comprising at least one closed pocket of a porous textile fabric; a source of air pressure; and a connecting means; said closed pocket having said connecting means connecting the interior of said closed pocket to said source of air pressure; said porous textile fabric permitting air seepage therethrough at approximately 12 cubic feet per minute; said air under positive pressure being derived from compressor means; said compressor means being mounted on top of said shrink tunnel,

4. The device substantially as set forth in claim 3 wherein saidresp ective flexible curtains are mechanically mounted at the top of said entrance openings and exit openings and are pivotable about said tops of said entrance openings and exit openings.

References Cited bythe Examiner UNITED STATES PATENTS 2,906,627 9/1959 Payton 53184 X 2,977,106 3/1961 Dulf 34242 3,156,812 10/1964 Forman et al 34-225 X WILLIAM F. ODEA, Primary Examiner.

NORMAN YUDKOFF, Examiner. V

W. C. EVERETT, C. R. REMKE, Assistant Examiners. 

1. A FLEXIBLE AIR COOLED CURTAIN FOR AN OPENING IN AN OVEN; SAID FLEXIBLE AIR COOLED CURTAIN COMPRISING A PLURALITY OF CLOSED POCKETS OF A POROUS TEXTILE FABRIC; SAID PLURALITY OF CLOSED POCKETS HAVING CONNECTING MEANS FOR CONNECTING THE INTERIOR OF SAID POCKETS TO A SOURCE OF AIR UNDER POSITIVE PRESSURE; SAID POCKETS BEING FORMED BY PARALLEL SEWN LINES EXTENDING FROM THE OPEN TOP OF A CLOTH BAG; SAID POROUS TEXTILE FABRIC PERMITTING AIR SEEPAGE THERETHROUGH AT APPROXIMATELY 12 CUBIC FEET PER MINUTE. 